A command from a missing directory fails ENOENT with no pane; one whose shell never started ends exit 127

Exec made a command pane in a directory that was not there, whose shell
never started: it said running for ever, a follower waited for an exit
that never came, and Kill found it. The line now fails up front, as Tty
does, `exec: <dir>: no such directory`; and a command pane whose shell
the host could not start ends `exit 127` at once. A shell that could not
start in its directory says `directory missing`, not `file not found`.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 5 insertions, 1 deletions

diff --git a/docs/fs.md b/docs/fs.md
index 49685888..dc3e7533 100644
--- a/docs/fs.md
+++ b/docs/fs.md
@@ -378,7 +378,11 @@ same tree without leaving the process.
   exits, `exit` typed or run, closes its pane). Nothing is ever typed over
   text someone typed at a prompt and did not send. From anywhere else -- a
   file, a scratch, a tag, a terminal with a line typed at its prompt or
-  whose tty a program holds -- it runs as a command pane: a
+  whose tty a program holds -- it runs as a command pane (from a pane whose
+  directory is not there it runs nothing and makes no pane, `exec: <dir>:
+  no such directory`, ENOENT, as `Tty` there does; one whose shell the host
+  cannot start ends at once, `exit <serial> 127` in the log, its tag no
+  longer running, nothing for Kill): a
   terminal whose child is the root ctl's `Shell` ($SHELL, else /bin/sh, unless set) run
   with `-c` and the line, in the pane's directory, with job control on
   (bash, sh, dash, zsh, ksh `-m`; fish `status job-control full`),